1. Field of the Invention
The present invention relates to a spindle motor, a disk drive apparatus, and an insertion method.
2. Description of the Related Art
Hard disk drives typically have spindle motors arranged to rotate disks installed therein. A known hard disk drive and a known spindle motor are described in, for example, JP-A 2006-040423. Paragraph of this publication states that the spindle motor (SPM) is fixed to a base of the hard disk drive (HDD). In addition, paragraph of the publication states that a low-density gas having a density lower than that of air, such as, for example, helium, is used as an atmosphere inside a hard disk assembly (HDA).
A case of the hard disk drive is arranged to be substantially airtight in order to keep an interior space thereof clean. In particular, the low-density gas, such as helium, tends to easily pass through even a minute gap. Therefore, in the case where an interior of the case is to be filled with the low-density gas as in the case of the hard disk drive described in JP-A 2006-040423, extremely high airtightness is required. In order to improve the airtightness of the case, it is preferable that the number of through holes defined in a base thereof is decreased.
Meanwhile, a bearing mechanism arranged to support a rotating portion of the spindle motor is fixed to the base of the hard disk drive. In order to fix the bearing mechanism without defining a through hole in the base, it is conceivable, for example, to provide a cup portion having a bottom and being cylindrical in the base, and insert and arrange the bearing mechanism in the cup portion. However, when the bearing mechanism is inserted into the cup portion having the bottom and being cylindrical, resistance against insertion of the bearing mechanism into the cup portion may be increased because gas cannot be discharged out of the cup portion. This will reduce efficiency in an assembling operation, and make it difficult to accurately position the bearing mechanism with respect to a base member.